To gain access to treatment sites in the body, catheters must be flexible enough to conform to and follow natural anatomical pathways as they are advanced. These soft and delicate tissue pathways can be quite tortuous with many twists and turns. In the vasculature, this is especially the case, and even more so in certain areas of the vasculature such as the vessels of the brain and the coronary arteries.
When treating a site in the vasculature, the state-of-the-art practice is to first gain access to the treatment site with a flexible, steerable guidewire. Such a guidewire can be precisely controlled by the physician and steered into place using radiographic guidance. Once the guidewire is in-place, a device, referred to generally as a catheter, is advanced over the guidewire. The catheter must be flexible enough to smoothly follow the pathway of guidewire. After traversing the guidewire to the treatment site, the catheter can be used to deliver the treatment.
In the case of arterial blockage, the catheter may be a balloon dilatation catheter that is used to open the blockage. In such an embodiment, the guidewire is, first, passed up to and through the lesion. Then, the catheter is advanced over the guidewire and through the lesion. It is preferable to pass the guidewire through the blockage without aid of another device. However, if the guidewire is not able to penetrate the blockage, other aids are needed.
Currently, treatment of CTOs by catheter interventionalists is performed by attempting to pass the guidewire across the CTO. Once the guidewire is across, a low profile balloon catheter can be advanced over the guidewire to dilate the lesion. Such a procedure is almost always followed by placement of a stent. Specialty guidewires are available to aid the physician in this effort but they, too, are limited in their utility by the constraints of flexibility and compliance. It is noted that attempting to cross CTOs is a tedious practice with current equipment and is met with limited success.
In instances where the guidewire is not able to penetrate the blockage, different devices must be used successively to pass through the blockage and, then, effect the treatment. In one prior art procedure, the guidewire is advanced up to the blockage. Then, a micro-lumen catheter is advanced over the guidewire and against the blockage. A CTO penetrating device, such as the device sold by Cordis Corporation and referred to as the FRONTRUNNER® XP CTO, is threaded through the lumen of the micro-lumen catheter and up to the blockage. The penetrating device is actuated to penetrate through the blockage. When complete penetration is established, the micro-lumen catheter is advance over the penetrating device and through the blockage. The penetrating device is removed and the treatment catheter (e.g., balloon expanding or stent placing) is advanced through or around the micro-lumen catheter such that the treatment site surrounds the portion of the catheter used for treatment. If disposed within the micro-lumen catheter, it is removed before treatment is effected (i.e., before expansion of the balloon). A stent may or may not be deployed after the penetration of the blockage is widened.
It would be beneficial to provide a catheter, catheter system, and treatment process that can advance a device up to the treatment site with sufficient flexibility through a tortuous path, that can be used to penetrate a CTO, and that can also be used as an exchange wire for receiving thereover the treatment catheter to be used for opening the CTO for treatment with balloons or stents, for example.